DMF-activated chlorosilane chemistry: Molybdenum-catalyzed reactions of R3SiH, DMF and R′3SiCl to initially form R′3SiOSiR′3 and R3SiCl

Article abstract of DOI:10.1016/j.ica.2017.06.010

The room temperature reactions between R₃SiH (R₃?=?Et₃, PhMe₂, Ph₂Me) and R′₃SiCl (R′₃?=?Me₃, PhMe₂, Ph₂Me), with an excess of dimethylformamide (DMF) in the presence of (Me₃N)Mo(CO)₅ as a catalyst, result in the initial formation of R₃SiCl, R′₃SiOSiR′₃ and Me₃N as detected by ²⁹Si, ¹³C, ¹H NMR spectroscopy and GC/MS. As the reaction proceeds, the more so if the reaction temperature is raised, mixed disiloxanes R₃SiOSiR′₃ and ultimately lesser amounts of R₃SiOSiR₃ may be detected. A mechanism involving the activation of chlorosilanes by the nucleophilic DMF is proposed to produce transient imminium siloxy ion pairs, [Me₂N[dbnd]CHCl]⁺[R′₃SiO]^? ? [Me₂N[dbnd]CH(OSiR′₃)]⁺Cl^? which react with R₃SiH to form Me₂NCH₂OSiR′₃ and R₃SiCl. A secondary reaction of Me₂NCH₂OSiR′₃ with R′₃SiCl produces the symmetrical disiloxane R′₃SiOSiR′₃ and ClCH₂NMe₂. The final stage of the reaction is the reduction of ClCH₂NMe₂ by R₃SiH, a reaction which is reported for the first time. The newly created chlorosilane R₃SiCl can become involved in the initial DMF activation chemistry thereby forming the other disiloxanes observed as the reaction proceeds.

Full text of DOI:10.1016/j.ica.2017.06.010

Inorganica Chimica Acta 466 (2017) 376–381
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Research paper
DMF-activated chlorosilane chemistry: Molybdenum-catalyzed
0
0
0
reactions of R SiH, DMF and R SiCl to initially form R SiOSiR and
3
3
3
3
R3SiCl
⇑
Paulina E. Gonzalez, Hemant K. Sharma, Keith H. Pannell
Department of Chemistry, The University of Texas at El Paso, El Paso, TX 79968-0513, USA
a r t i c l e i n f o
a b s t r a c t
0
0
3
Article history:
3 3 3 2 2 3 3 2
The room temperature reactions between R SiH (R = Et , PhMe , Ph Me) and R SiCl (R = Me , PhMe ,
Received 12 April 2017
Received in revised form 4 June 2017
Accepted 7 June 2017
Ph
2
Me), with an excess of dimethylformamide (DMF) in the presence of (Me
3
N)Mo(CO)
5
1
as a catalyst,
0
0
29
13
result in the initial formation of R
3
SiCl, R
3
SiOSiR
3
and Me
3
N as detected by Si, C, H NMR spec-
troscopy and GC/MS. As the reaction proceeds, the more so if the reaction temperature is raised, mixed
Available online 12 June 2017
0
disiloxanes R
3
SiOSiR
3
and ultimately lesser amounts of R
3
SiOSiR
3
may be detected. A mechanism involv-
ing the activation of chlorosilanes by the nucleophilic DMF is proposed to produce transient imminium
+
0
ꢀ
0
+
ꢀ
siloxy ion pairs, [Me
2
N@CHCl] [R
3
SiO] ꢀ [Me
2
N@CH(OSiR
3
)] Cl which react with R
3
SiH to form
SiCl produces the symmetri-
NMe by
SiCl can become
0
0
0
Me
2
NCH
2
OSiR
3
0
and R
3
SiCl. A secondary reaction of Me
and ClCH
SiH, a reaction which is reported for the first time. The newly created chlorosilane R
2
NCH
2
OSiR
3
with R
3
0
cal disiloxane R
3
SiOSiR
3
2
NMe
2
. The final stage of the reaction is the reduction of ClCH
2
2
R
3
3
involved in the initial DMF activation chemistry thereby forming the other disiloxanes observed as the
reaction proceeds.
Ó 2017 Elsevier B.V. All rights reserved.
1
. Introduction
[2c] and –stannanes [2c] to form the corresponding disiloxanes,
siloxygermanes and siloxystannanes, respectively, Eq. (2).
Subsequent to seminal discoveries by the Voronkov group [1a],
the metal-catalyzed reduction of amides by silanes, R SiH, to form
amines has become a very popular synthetic route due in part to
the mild reaction conditions required [1]. We recently proposed
that the (Me N)Mo(CO) -catalyzed use of tertiary silanes as
3 5
reductants for amides, specifically dimethylformamide (DMF), pro-
0
0
3
R SiOCH NMe þ R ECl ! R SiOER þ ClCH NMe
3
2
2
3
2
2
ð2Þ
3
3
0
3
= A variety of Ph, Me, Et, Bu; E = Si, Ge, Sn.
R
3
, R
The chemistry in Eq. (2) is effectively instantaneous, requires no
catalyst, and in the solvents used for the transformation, the sec-
ondary product ClCH NMe precipitates from solution thus making
ceeded via an initial hydrosilylation step to yield siloxymethy-
2
2
lamine intermediates,
3 2 2
R SiOCH NMe , 1 [2a]. Subsequently
product separation facile. The literature reveals few simple reac-
tions whereby mixed disiloxanes of the type R
readily obtained in a high yield one-step reaction with readily
available reagents [5].
we isolated and characterized such materials, Eq. (1) [2b]. These
intermediates may then undergo a second reaction with a silane
to form trimethylamine and the corresponding disiloxane.
0
3
SiOSiR
3
can be
The isolation of 1 signifies that the first step in Eq. (1) is faster
than the second step, hence we reasoned that a one-pot reaction
2
R
3
SiH þ Me
2
NCðOÞH ! R
3
SiH þ R
SiOSiR
A single example of such a compound, Me
3
SiOCH
2
NMe
2
ð1Þ
involving a silane, R
3
SiH, DMF and the Mo catalyst, and a
!
R
3
3
þ Me
3
N
ð1Þ
0
chlorosilane, R
3
SiCl, could provide a simple and efficient route to
3
SiOCH
2
NMe
2
, 1a,
mixed disiloxanes, Scheme 1. The chlorosilane effectively hijacks 1
to form the targeted disiloxane. Throughout the report we designate
the starting SiH and SiCl reagents as red and blue, respectively.
We now report the results from a series of such reactions that
indeed do result in disiloxane formation, but primarily that from
was reported in 1981 by the Mironov group via the condensation
of trimethylsilylamine, Me SiNMe , with formaldehyde [3]. The
same group [4], and later ourselves [2c], illustrated the capacity
of such compounds to react with chloro-silanes [4,2c], –germanes
3
2
0
0
3
the initial chlorosilane, R SiOSiR , thereby illustrating a new and
3
⇑
Corresponding author.
E-mail address: kpannell@utep.edu (K.H. Pannell).
unexpected chemistry involving activation of the chlorosilane by
DMF.
http://dx.doi.org/10.1016/j.ica.2017.06.010
020-1693/Ó 2017 Elsevier B.V. All rights reserved.
0

P.E. Gonzalez et al. / Inorganica Chimica Acta 466 (2017) 376–381
377
and cannot be used for quantitative analysis, where the NMR tech-
nique is superior [6].
Using the same starting silane, Et
MeSiCl, the RT reactions produced essentially the same chemi-
cal result, predominant formation of the disiloxane stemming from
3 2
SiH, but using PhMe SiCl and
Ph
2
0
0
the initially present chlorosilane, i.e. R
3
SiOSiR
3
, together with
0
Et
3
SiCl, and smaller amounts of the mixed disiloxane R
3
SiOSiEt
3
.
0
In all cases R
3
SiCl was also present at the end of the 50 °C
reactions. The quantitative data for these results, and those
obtained from maintaining Me SiCl constant while changing
3
R SiH, are presented in Table 1 and displayed graphically in Fig. 3.
3
Scheme 1. Proposed route to mixed disiloxanes.
2
9
13
A typical Si and C NMR monitoring sequence for the Et
Me PhSiCl, and the Me PhSiH/Me SiCl systems are presented in
Fig. S1a and S2a of the supplementary material. The final H
3
SiH/
2
2
3
1
2
. Results and discussion
NMR spectra are also presented as Fig. S1b and S2b, as typical of
the determination of the relative yields of the disiloxanes.
The nature of the chlorosilane and hydrosilane had a relatively
small impact upon the general trend of the product distribution;
however, it did impact both the time periods for reactions at RT
and the actual percentages of product formation. These percentage
product formations reflect kinetic aspects beyond the scope of this
report.
A typical reaction involving equimolar amounts of Et
SiCl, together with a 5-fold excess of DMF, catalyzed by
N)Mo(CO) (5 mol%), was monitored in a C solution by
NMR spectroscopy, Fig. 1.
At room temperature, RT, the reaction results in the ultimate
formation of Et SiCl and Me SiOSiMe as the major products after
days, Fig. 1 (left). Repeating the reaction at 50 °C resulted in a
3
SiH and
Me
3
(
Me
3
5
6 6
D
3
3
3
6
complete reaction after a few hours, Fig. 1 (right). However, at
the higher temperature, the two other possible disiloxanes,
We also performed a series of experiments in which the silane,
0
3
R3SiH, and chlorosilane, R SiCl, substituents were exchanged.
Me
in slightly higher amounts than at RT, but still minor quantities
compared to Me SiOSiMe . Also, as noted, Me SiCl was present at
3
SiOSiEt
3
and Et
3
SiOSiEt
3
were formed along with Me
3
SiOSiMe
3
,
Thus, whereas the relative amounts of R
0
3SiOSiR 3
0
, R
0
3SiOSiR3,
R3SiOSiR3 for the reactions involving Et SiH and Ph MeSiCl
3
2
3
3
3
(PhMe SiCl) were 61% (76%), 23% (34%), and 16% (0%), the results
2
the end of the high temperature reaction. Prolonged reaction times
from the interchanged system of Ph MeSiH (PhMe SiH) and Et SiCl
2
2
3
at either temperature for ꢁ20 days did not alter the product
were 25% (22%), 36% (33%) and 39% (45%). These variations in the
relative amounts of the products are significant, but neither an
explicable trend nor clear synthetic utility for mixed disiloxanes
is apparent at this time.
We studied the possible impact of having significantly less DMF
present in the reaction and observed very little effect of such a
1
3
composition.
C NMR spectroscopy confirmed that the only
non-silicon containing product was Me
A GC/MS analysis of the final reaction mixture confirmed the
presence of all products, except Me N. As has been observed previ-
ously this technique is a supplementary tool for siloxane analysis
3
N, Fig. 2.
3
Fig. 1. 29Si NMR monitoring of the reaction of Et
Et SiCl = 36.0 ppm; Me SiOSiMe = 6.8 ppm; Me SiOSiEt
2,5].
SiH, Me
SiCl, DMF and the Mo catalyst at RT (left) and at 50 °C (right): Et
SiOSiEt = 8.7 ppm. In all cases in this article the NMR data are in accord with published data
3
3
3 3
SiH = 0.0 ppm; Me SiCl = 30.8 ppm;
3
3
3
3
3
= 6.2, 9.4 ppm; Et
3
3
[

3
78
P.E. Gonzalez et al. / Inorganica Chimica Acta 466 (2017) 376–381
Fig. 2. 13C NMR monitoring of the reaction of Et
at RT (left) and at 50 °C (right), showing the presence of Me
3
SiH, Me
3
SiCl, DMF and catalyst in C
6
D
6
3
N at ꢁ47 ppm.
Table 1
Amounts of disiloxanes (%) obtained from the reactions of R
reactions were monitored at RT, 50 °C, and from RT to 50 °C. The time noted is for complete removal of R
0
0
3
= Me
3
SiH/Me
3
SiCl: R
3
= PhMe
2
(1); Ph
2
Me, (2); and Et
SiH.
3
SiH/R
3
SiCl (R
3 3 2 2
(3); Et (4); PhMe (5); Ph Me (6). The
3
0
0
0
0
3
R SiOSiR
R
3
SiH/R
PhMe
Ph Me
Me
Et
PhMe
3
SiCl
R
3
SiOSiR
3
3
R
3
SiOSiR
3
Temp.
Time
1
2
3
4
5
6
2
50
60
85 (60)
35
34
15 (21)
100
34
15
6
0 (19)
RT
RT
RT (50)
RT ? 50
RT ? 50
RT ? 50
8d
17d
6d (3 h)
21 h ? 3 h
3 h ? 6 h
15d ? 4 h
2
3
3
2
76
61
0
16
Ph
2
Me
23
A typical reaction involved addition of independently synthe-
sized Et SiOCH NMe , 1b, to a mixture of Et SiH and Me SiCl and
3
2
2
3
3
2
9
13
monitoring the subsequent reaction by Si and C NMR spec-
troscopy, Fig. 4.
The reaction was performed at room temperature for the first
2
2 h, and subsequently at 50 °C. The immediate formation of a
white precipitate of ClCH NMe was observed at RT, and NMR
monitoring illustrated the presence of Et SiCl, unsymmetrical
disiloxane (Et SiOSiMe ) and traces of Me SiOSiMe . There was a
clear absence of the initially added Et SiOCH NMe , which as
previously reported should react immediately with Me SiCl to
form Et SiOSiMe and ClCH NMe , as the spectral and visual
analyses of the experiment demonstrates.
The white solid, ClCH NMe , remained present during the 22 h
2
2
3
3
3
3
3
3
2
2
3
3
3
2
2
0
0
0
Fig. 3. Relative yields of the disiloxanes (R
3
SiOSiR
3
,
R
3
SiOSiR
3
,
R
3
SiOSiR
3
)
obtained from the reactions of R SiH/Me SiCl (R
3
3
3
= PhMe
2
, Ph
2
Me); and Et
3
SiH/
2
2
0
0
3
= Me
R
3
SiCl (R
3 2 2
, PhMe , Ph Me).
the reaction was maintained at room temperature, during which
time the NMR spectra were unchanged. When the reaction mixture
was heated at 50 °C (2–5 h) significant physical and NMR spectro-
scopic changes were observed; the solid progressively vanished,
change of reaction conditions. For the reaction of Et
and DMF with equimolar amounts of reagents the Me
Me SiOSiEt , Et SiOSiEt product distribution at RT was 78%, 22%
3
SiH, Me
3
SiCl
3
SiOSiMe
3
,
13
3
3
3
3
along with the NMR signals for Et SiH. Concomitantly the
3
C
and 0%, ꢁ identical to the result with a 5 M excess of the DMF,
3
NMR peak at 47 ppm due to Me N appeared and progressively
2
9
Table 1, entry 3.
increased along with the Si signal for Et SiCl. At the end of the
3
The results above summarize the chemical outcome from the
various experiments performed; however, equally important are
those features of the chemistry that we do not observe. For exam-
reaction, very little solid material was present and all the Et SiH
3
had vanished to be replaced by Et SiCl, i.e. at the ‘‘elevated” tem-
3
perature of 50 °C, Et SiH has the capacity to reduce ClCH NMe
2
3
2
ple, since the reduction of DMF by Et
3
SiH to form Me
3
N was appar-
to Me N, a previously unknown chemistry, Eq. (4). The reduction
3
ent, but no intermediacy of siloxymethylamine was observed, we
performed experiments to evaluate the possible rôle of this mate-
rial, if indeed it was formed, in our one pot reaction, Eq. (3).
will proceed in the absence of the Mo catalyst to a limited extent
at the elevated temperature but only after a time period of
ꢁ2–3 days. The reduction of ClCH NMe
2
2
3
by Et SiH is
directly related to its reaction with silylphosphines to form
aminomethyl)phosphines and chlorosilanes, Eq. (5) [7].
DMF
Et
3
SiOCH
2
NMe
2
þ Et
3
SiH þ Me
3
SiCL
ꢀ!
?
ð3Þ
(
ðMe
3
NÞMoðCOÞ5

P.E. Gonzalez et al. / Inorganica Chimica Acta 466 (2017) 376–381
379
Fig. 4. 29Si NMR (left) and 13C NMR (right) monitoring of the reaction of Et
0 °C (t denoted in red color).
, Et
SiH, Me
at RT for 22 h plus another extra t hours at
3
SiOCH
2
NMe
2
3
3
SiCl, DMF and catalyst in C
6
D
6
5
Et
Et
3
3
SiH þ ClCH
2
NMe
2
! Et
3
SiCl þ CH
3
NMe
2
ð4Þ
ð5Þ
powerful nucleophilic solvent. For example, whereas the
MeSiCl /DMSO reagent is very useful for chlorination of enamides
and enecarbamates, use of DMF in place of DMSO resulted in no
3
SiPR
2
þ ClCH
2
NMe
2
! Et
3
SiCl þ Me
2 2 2
NCH PR
chlorination [10]. The Bassindale group has reported 29Si and
NMR spectroscopic evidence suggesting that Me SiCl may very
weakly interact with DMF to form equilibria involving Me NCH
)] [Cl] [11]. Such species were invoked to explain the
DMF-enhanced hydrolysis of chlorosilanes [12a]; the ready
13
C
Thus, despite our inability to observe the intermediacy/forma-
tion of either Et SiOCH NMe or ClCH NMe in the molybdenum-
catalyzed reactions of Et SiH, Me SiCl and DMF, their transient for-
mation and reactivity is explained. The generalized Scheme 1, out-
lined at the beginning, can be modified to Scheme 2, incorporating
the unexpected formation of both Me
However, our general inability to experimentally observe signif-
icant amounts of the mixed disiloxane, Et SiOSiMe , and the pre-
dominant formation of Me SiOSiMe suggests that other
processes are occurring. The Bellesia group, and others, have estab-
lished that chlorosilanes react with DMSO to form transient chloro-
sulfonium/siloxyl ion pairs, [Me
reagent (Me
of carbon-chlorine bonds in a variety of organic substrates, with
concomitant siloxane formation [9]. However, these examples of
Si-Cl activation are not exhibited by DMF, a useful but much less
3
3
2
2
2
2
2
3
3
+
ꢀ
(
OSiMe
3
0
00
racemization of chiral organosilanes, RR R SiX [12b]; cryoscopic
measurements on chlorosilanes in DMF [13]; and patent reports
3 3
N and Et SiCl.
of the DMF-catalyzed reaction of propyltrichlorosilane with Ac
to synthesize propyltriacetoxysilane [14]. Additionally, trichlorosi-
lane-dimethylformamide (Cl SiH-DMF) is an effective reducing
2
O
3
3
3
3
,
3
agent for reduction of aldehydes and imines in which hypervalent
silicates were proposed as active species [15].
We now propose that the chemistry described herein is initi-
ated via chlorosilane/DMF interactions leading to low equilibrium
concentrations of chloroimminium siloxyl ion pairs or their various
+
ꢀ
2
SCl] [R
n
Cl2ꢀnSiO] [8,9], and the
3
SiCl/DMSO) has been widely used for the formation
other forms, Scheme 3. In our hands the Me
3
SiCl/DMF system, even
at elevated temperatures in the presence of the Mo catalyst,
Scheme 2. Possible mechanism for mixed disiloxane formation coupled to trans-
3
Scheme 3. Initial ion-pair formation, and reactivity, from the reaction of Me SiCl
formation of Et
3
SiH into Et
3
SiCl and Me
3
N formation.
with DMF.

3
80
P.E. Gonzalez et al. / Inorganica Chimica Acta 466 (2017) 376–381
exhibits no observable reaction and the starting materials are
Me
3
SiOSiMe
3
þ Et
3
SiCl ! MeSiOSiEt
3
þ Me
3
SiCl
ð9Þ
unchanged. The reducing silane, Et
to force the chemistry forward.
3
SiH, is a needed co-reactant
Examination of the spectral data in Fig. 1 obtained at RT, which
includes the predominant formation of both Et SiCl and
Me SiOSiMe3, and absence of Me SiCl, thus seems counterintuitive.
Therefore we have repeated the chemistry outlined in Eq. (9),
under the conditions of our chemistry, Et SiH, Me SiOSiMe
, DMF, and (Me N)Mo(CO) at RT and 50 °C. No significant silyl
3
The Et
Me SiOCH
3
SiH will reduce the Me
3
SiOCHClNMe
2
species to
SiCl, Eq. (6).
3
3
3
2
NMe with concomitant formation of Et
2
3
The newly formed siloxymethylamine will react with Me
form Me SiOSiMe and ClCH NMe
3
SiCl to
3
3
3
,
3
3
2
2
.
6
C D
6
3
5
exchange chemistry was observed at room temperature over the
time periods used in our study. However, at the elevated tempera-
ture there is an equilibrium set up in a few hours which replicates
the relative amounts of the products observed in our experiments
at that temperature.
Me
3
SiOCHClNMe
2
þ Et
3
SiH ! Et
3
SiCl þ Me
3
SiOCH
2
NMe
2
ð6Þ
Related silane reductions have been reported for nitrillium
salts, and dialkylaminochlorocarbenium salts, Eqs. (7) and (8) [16]
þ
ꢂꢀ þ Et
½
½
EtNCRꢂ ½BF
4
3
SiH ! Et
3
SiF þ ½EtN@CHRꢂ þ BF
3
ð7Þ
The Voronkov study, Eq. (9), reported a high yield of both
Me
However, we are using a closed system and not isolating the prod-
ucts and assume that in their system, where the Me SiCl is the low
3 3 3
SiCl and Et SiOSiMe which is not congruent with our results.
þ
ꢀ
ðMe
!
2
NÞ @CClꢂ Cl þ MePh
2
SiH
2
þ
ꢀ
½ðMe
2
NÞ @CHꢂ Cl þ MePh
2
SiCl
ð8Þ
3
2
temperature distillation product, this progressive removal will
constantly drive the equilibrium process to completion.
Finally, as noted above, ClCH
equivalent of Et
duct, Me
2 2
NMe will be reduced by a second
3
SiH to produce the observed final reduction pro-
N, and another equivalent of Et SiCl. The overall process
is outlined in Scheme 4 for the reaction of Et SiH and Me SiCl.
3 3
We also studied the chemistry of the Et SiH/Me SiI/DMF
3
3
system. While the overall results are in agreement with the data
outlined and discussed above, there is a single and important
distinction, the reaction is extremely slow. At room temperature
there is only minimal reaction after 16 days! At the elevated
3
3
Since there is a hydrosilane to chlorosilane transformation
during the reaction, as the reaction proceeds there is a build-up
of Et
disiloxane (Et
Me SiOCH NMe
increases it can also participate in the initial imminium salt
3
SiCl, which can participate in the formation of mixed
SiOSiMe ) by reaction with the initially formed
. Furthermore, as the amount of Et SiCl further
5
0 °C temperature the reaction was complete after the same time
3
3
period. This would be in accord with the reduced nucleophilicity
ꢀ
3
2
2
3
of the I species in the initially formed siloxyimminium species.
Finally there is the possibility that some direct H/Cl exchange is
taking place between the starting hydrosilanes and chlorosilanes
+
ꢀ
2 3
formation reaction to produce [Me N@CHCl] [Et SiO] and in this
manner there will be a limited formation of the symmetrical
disiloxane derived from the initially used triethylsilane, i.e.
perhaps catalyzed by the (Me
3
N)Mo(CO)
5
. In none of the experi-
0
ments did we observe the formation of any R
experiments a mixture of Et SiH and Me
3
SiH. In separate
Et
analysis illustrated in Fig. 1, except that in the low temperature
experiment no Et SiOSiEt is observed. The relative amounts of
the three disiloxane products formed (Me SiOSiMe , Me SiOSiEt
and Et SiOSiEt ) will be dependent upon kinetic issues beyond
3 3
SiOSiEt . Exactly such an outcome is noted from the NMR
3
3
SiCl in the presence of
the catalyst was monitored over the time periods involved in the
reaction conditions noted above, and no exchange was observed.
3
3
3
3
3
3
,
However, a spectral analysis of a >1 year old sample of an Et
3
SiH/
3
3
Me SiCl experiment did illustrate and small amount of such an
3
the current scope of this report. However, for the examples we
studied using variations of silane (R
starting materials, the generally observed amounts of product, and
their time of appearance,
Fig. 3, are in accord with our proposed mechanism.
exchange, Fig. S3. The length of time required for such an exchange
0
3
SiH) and chlorosilane (R
3
SiCl)
excludes it from having a rôle in the chemistry reported herein,
0
independent of not observing any R
3
SiH.
0
0
0
R SiOSiR > R SiOSiR > R SiOSiR ,
3 3 3 3 3
3
3
. Conclusions
The differing results noted at RT and 50 °C, in terms of
disiloxane proportions and residual presence of initial chlorosi-
0
0
3
The interactions between chlorosilanes R
tions of Me , Et , PhMe and Ph Me) and DMF form low equilib-
rium concentrations of chloroimminium siloxyl ion pairs,
3
SiCl (R = combina-
0
lanes, R
3
SiCl, were an object of concern. The Voronkov group, have
3
3
2
2
reported reactions between disiloxanes and chlorosilanes
involving high yield exchange of silyl groups, e.g. Eq. (9) [17].
+
0
ꢀ
[
Me
reducing agent, R
react to initially form R
2
N@CHCl] [R
3
SiO] . When formed in the presence of a silane
SiH, and a Mo catalyst, (Me N)Mo(CO) , they
SiCl. The newly
3
3
5
0
0
3
3
3 3
SiOSiR , Me N and R
formed chlorosilane can enter into the reaction cycle and secon-
0
darily form the mixed disiloxane R
SiOSiR
the Mo catalyst, silanes R
Eschenmoser’s salt, to Me
3
SiOSiR
3
, and ultimately also
R
3
3
. We have also demonstrated that, in the presence of
SiH can efficiently reduce ClCH NMe
N with concomitant formation of R SiCl.
3
2
2
,
3
3
Finally, we clarify the reported reactions between disiloxanes and
chlorosilanes involving high yield exchange of silyl groups.
4
. Experimental
All manipulations were carried out under an argon (or nitrogen)
atmosphere using Schlenk or vacuum line techniques. Hydrosi-
lanes, chlorosilanes, and Me SiI, were purchased from Gelest and
distilled prior to use; C and CDCl were purchased from Cam-
bridge Isotope Laboratories, Inc.; Et SiOCH NMe [2] and Mo(CO)
NMe [18] were synthesized by the reported methods. NMR
spectra were recorded on either a JEOL 600 MHz or Bruker
300 MHz spectrometer in C
3
6
D
6
3
3
2
2
5
-
3
Scheme 4. Overall scheme proposed for the formation of initially observed
products, [M] = catalyst.
6 6
D .

P.E. Gonzalez et al. / Inorganica Chimica Acta 466 (2017) 376–381
381
In a typical experiment, a Pyrex NMR tube was charged with
(j) C. Cheng, M. Brookhart, J. Am. Chem. Soc. 134 (2012) 11304–11307;
(k) B. Li, J.-B. Sortais, C. Darcel, Chem. Commun. 49 (2013) 3691–3693;
l) A. Volkov, E. Buitrago, H. Adolfsson, Eur. J. Org. Chem. 11 (2013) 2066–2070.
2] (a) H.K. Sharma, K.H. Pannell, Angew. Chem. Int. Ed. 48 (2009) 7052–7054;
(b) R. Arias-Ugarte, H.K. Sharma, A.L.C. Morris, K.H. Pannell, J. Am. Chem. Soc.
134 (2012) 848–851;
ꢀ4
ꢀ4
Et
3
SiH (0.10 g, 8.6 ꢃ 10
moles), Me
3
SiCl (0.094 g, 8.6 ꢃ 10
NMe (0.013 g,
6 6
D . The NMR tube was sealed
(
ꢀ3
moles), DMF (0.32 g, 4.31 ꢃ 10 moles), Mo(CO)
5
3
[
ꢀ5
4
.31 ꢃ 10 moles) and 0.3 mL of C
2
9
under vacuum and the subsequent reaction monitored by Si,
(
c) H.K. Sharma, R. Arias-Ugarte, D. Tomlinson, R. Gappa, A.J. Metta-Magaña, H.
Ito, K.H. Pannell, Organometallics 32 (2013) 3788–3794.
[3] V.F. Mironov, V.P. Kozyukov, V.P. Kozyukov, Zh. Obshch. Khim. 51 (1981)
382–2383.
4] V.P. Kozyukov, V.P. Kozyukov, V.F. Mironov, Zh. Obshch. Khim. 53 (1983) 119–
26.
1
3
1
C, and H NMR spectroscopy. The NMR tube was either main-
tained at RT or 50 °C (in an oil bath), or, as in the cases noted, at
RT followed by a period of t h at 50 °C Mo(CO) NMe (0.013 g,
.31 ꢃ 10 mol). In all cases monitoring was ceased at such time
as the R SiH had been consumed.
2
5
3
[
ꢀ5
4
1
3
[5] (a) J. Chojnowski, S. Rubinsztajn, J.A. Cella, W. Fortuniak, M. Cypryk, J. Kurjata,
K. Kazmierski, Organometallics 24 (2005) 6077–6084;
(
b) R. Abele, E. Abele, M. Fleisher, S. Grinberga, E. Lukevics, J. Organomet. Chem.
Acknowledgements
686 (2003) 52–57.
[
[
6] M. Peng, D. Lu, J. Liu, Y. Yang, Zhongguo Yiyao Gongye Zazhi 44 (2013) 66–69.
7] A.A. Prishchenko, M.V. Livantsov, O.P. Novikova, L.I. Livantsova, V.S. Petrosyan,
Heteroatom Chem. 21 (2010) 441–445.
We thank the Welch Foundation, Houston TX., for support of
this research via Grant AH-0546.
[8] (a) F. Bellesia, F. Ghelfi, U.M. Pagnoni, J. Chem. Res. (1987) 24–25;
(
(
b) F. Bellesia, F. Ghelfi, U.M. Pagnoni, A. Pinetta, J. Chem. Res. (1987) 238–239;
c) F. Bellesia, F. Ghelfi, R. Grandi, U.G. Pagnoni, A. Pinetti, J. Hetero. Chem. 30
Appendix A. Supplementary data
(1993) 617–621;
(
(
d) D.C. Snyder, J. Am. Chem. Soc. 60 (1995) 2638–2639;
e) P. Lu, J.K. Paulasaari, W.P. Weber, Organometallics 15 (1996) 4649–4652.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2017.06.010.
[
9] P.S. Vankar, M.V.R. Reddy, Y.D. Vankar, Org. Prep. Proc. Int. 30 (1998) 373–400.
[10] D. Lin, K. Cheng, X. Lu, J. Sun, Synlett 18 (2009) 2961–2964.
11] A.R. Bassindale, T. Stout, J. Organomet. Chem. 238 (1982) C41–C45.
[
[
12] (a) R.J.P. Corriu, G. Dabosi, M. Martineau, J. Organomet. Chem. 150 (1978) 27–
38;
References
(
4
b) R.J.P. Corriu, G. Dabosi, M. Martineau, J. Organomet. Chem. 154 (1978) 33–
3.
[
1] (a) L.I. Kopylova, N.D. Ivanova, M.G. Voronkov, Zh. Obshch. Khim. 55 (1985)
649–1651;
[
13] A.Ya. Deich, L.M. Chemokhud, Latvijas PSR Zinatnu Akademijas Vestis, Kim.
Ser. 5 (1974) 560–562.
14] B. Standke, J. Monkiewicz, A.-J. Frings, P. Jenkner, B. Trautvetter, M. Horn, Ger.
Offen. 2000, DE 19837010 A1 20000217.
15] S. Kobayashi, M. Yasuda, I. Hachiya, Chem. Lett. 25 (1996) 407–408.
16] (a) J.L. Fry, R.A. Ott, J. Org. Chem. 46 (1981) 602–607;
1
(
(
(
b) Y. Motoyama, K. Mitsui, T. Ishida, H.H. Nagashima, J. Am. Chem. Soc. 127
2005) 13150–13151;
c) S. Hanada, Y. Motoyama, H. Nagashima, Tetrahedron Lett. 47 (2006) 6173–
[
[
[
6
(
4
(
9
(
1
177;
d) K. Matsubara, T. Iura, T. Maki, H. Nagashima, J. Org. Chem. 67 (2002) 4985–
988;
e) S. Zhou, K. Junge, D. Adis, S. Das, M. Beller, Angew. Chem. Int. Ed. 48 (2009)
507–9510;
f) S. Das, D. Addis, S. Zhou, K. Junge, M. Beller, J. Am. Chem. Soc. 132 (2010)
770–1771;
(
b) V.D. Sheludyakov, Z.V. Belyakova, V.M. Shevchenko, E.A. Chernyshev, Russ.
Chem. Bull. 46 (1997) 997–1002.
[
17] (a) M.G. Voronkov, S.F. Pavlov, E.I. Dubinskaya, Dok. Akad. Nauk SSSR 227
(
(
(
1976) 362–365;
b) M.G. Voronkov, M.V. Romanova, E.I. Dubinskaya, Zh. Obshch. Khim. 73
2003) 1156–1157.
(
(
(
g) S. Das, D. Addis, K. Junge, M. Beller, Chem. Eur. J. 17 (2011) 12186–12192;
h) D. Miles, J. Ward, D.A. Foucher, Macromolecules 42 (2009) 9199–9203;
i) S. Park, M. Brookhart, J. Am. Chem. Soc. 134 (2012) 640–653;
[
18] W. Strohmeier, J.F. Guttenberger, H. Blumenthal, G. Albert, Chem. Ber. 99
1966) 3419–3424.
(